Today's construction site is designed by an architect. The architect's designs are copied to blueprints and transmitted to the contractor. The contractor will stake the area, i.e., survey the undeveloped area and place stakes at predetermined positions. The contractor, by comparing the architect's plans and the results of the survey, will determine the amount of dirt that needs to be removed or placed at each marker to meet the design plans.
After this process, earthmoving machines, e.g., bulldozers, scrapers, or excavators, are used to remove or fill the areas around the stakes. An unprocessed island is left remaining around the stake. After all the areas have been processed, the site is surveyed once again to confirm that the processed site meets the design specifications.
The above process requires large amounts of manual labor. The site has to be surveyed, staked, molded and surveyed once again. Furthermore, only a highly trained operator can efficiently operate the machine to obtain the desired degree of accuracy.
Laser systems have been used in order to provide a reference to the operator in performing this process. Typically, the laser system emits a beam of light which is swept over the site in a plane. The machine must be equipped with a suitable receiver. The system is able to give the operator an indication of the height of the machine and/or work implement.
However, there are certain limitations in present laser systems. First, present day systems rely on a number of reference stations which produce laser beams. Each of the reference stations must be place at a pre-surveyed position. The reference station cannot be moved without surveying in a new position. This limits the systems' usefulness because the survey process is time consuming. In addition, the reference stations must be placed at a location which is not subject to change. Otherwise a new location will have to be surveyed. Also, the present systems are limited in that without surveying new locations for the reference stations, the systems range is limited to the range of the laser and detectors.
Furthermore, the site plan must be defined with a fixed reference system. In order to determine position relative to the fixed reference system, the location of the reference station must be known within the fixed reference system. In known systems, the location of each reference station must be manually surveyed. In addition, the reference station cannot be moved without surveying the new location.
Other systems have used positioning systems directly on the various machines. For example, satellite systems enable a user with a specialized receiver to receive transmitted signals and using triangulation methods enable a user to determine position. However at a work site, this would require equipping each work machine that was processing the site with an expensive receiver.
The present invention is directed to overcoming one or more of the problems, as set forth above.